Ermm... the same reason I hum children show theme tunes! (Cos my hubby puts them on for the Bubba - over here in the UK we got this programme called the Zinzilla's and I keep singing that, and 64 Zoo Lane and Timmy Time)

The next day the whistling ended up turning into a godawful smell that combined bad fish and sewage. Perils of New England living. I'll take Sesame Street over that any day. Or even the Muppet Babies theme song...just make the bad smell go far, far away...